Woven conductor and method of forming the same



April 16, 1968 s} RASK WOVEN CONDUCTOR AND METHOD OF FORMING THE SAME 5Sheets-Sheet l Filed.Aug. 9, 1965 L O L lL M2 AUOENE) April 16, 1968 S.RASK 3,378,629

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April 16, 1968 s. RASK 3,378,629

WOVEN CONDUCTOR AND METHOD OF FORMING THE SAME Filed Aug. 9, 1965"" 5Sheets-Sheet 3 Ill jl/l/IIII INVENTOR. .Szan/ey 2 4 United States Patent3,378,629 WOVEN CONDUCTOR AND METHOD OF FORMING THE SAME Stanley Rask,New York, N.Y., assignor to Continental This invention relates to awoven matrix comprising both conducting and insulating warp members andconducting and insulating fill members in which the conductive fillmembers are woven into direct contact with each other at nodal pointsspaced apart at predetermined locations on the fabric.

The concept of a matrix system of interweaving wires and dielectricfibers, or yarns, has been employed heretofore in providing a basicstrip of fabric to which electrical components can be connected and inwhich certain of the wires running in one direction can be joined towires running in a perpendicular direction to form interconnectionsbetween the electrical components. In such woven circuits one of theimportant points is to make the inter-connections between wires assimple as possible, and in accordance with that requirement, the presentinvention provides for weaving the wire conductors and dielectric yarnsin a predetermined pattern such that, at nodal points where the wiresare to be interconnected, those running in one direction aredeliberately brought up through the dielectric yarns and crossed overthose running in the perpendicular direction. It is equally importantthat, at other points of near inter-section between perpendicular wires,there must be a layer of dielectric yarn between the wires to insulatethem from each other, and the present invention provides for thisinsulating layer. The dielectric yarn is of material capable ofwithstanding soldering temperatures so that all that is necessary tocreate the inter-connections is to run the Woven fabric through a hotsolder bath or a wave or jet solder ing device in which the nodal pointswill be automatically ioined together by the solder. Thereafter thefabric may be treated with a suitable material to retain the separa tionbetween other points of the wire conductors, and then electric terminalsor components or connectors may be attached to selected wires to form afinished circuit or cable.

The invention will be described in greater detail in connection with thedrawings in which:

FIG. 1 shows a section of a strip of woven circuit fabric as it comesfrom the loom;

FIG. 2 is a simple electrical circuit;

FIG. 3 shows the components of the circuit of FIG. 2 arranged forconnection by means of a wire matrix;

FIG. 4 shows a more complex electrical circuit diagram;

FIG. 5 is a schematic representation of a matrix circuit equivalent ofthe circuit in FIG. 4;

FIG. 6 is a pictorial representation of the circuit of FIGS. 4 and 5;

FIG. 7 is a simplified schematic representation of a cross-section ofthe cloth of FIG. 1; I

FIGS. 8-11 are simplified schematic representations of cross sections ofthe fabric of FIG. 1 at successive steps in the weaving thereof; and

FIG. 12 is a perspective, phantom view of a section of an electronicdevice incorporating woven circuits.

FIG. 1 shows an embodiment of the woven circuit fabric of this inventionprepared as an elongated, rather narrow strip, somewhat similar inappearance to a seat belt. However, there is no limit in theory as tothe width of the fabric and it could be made as wide as available loomsare capable of producing.

Patented Apr. 16, 1968 In textile weaving, the yarn running the lengthof the fabric is called the warp. The yarn inserted by a shuttle acrossand at right angles to the warp is known as the weft, or fill. Automaticlooms are well-known in the weaving industry which provide for holdingthe warp strands in separate headles independently of each other andshifting them so that the warp yarns are raised and lowered selectivelyto permit shuttles to be inserted selectively to produce any desiredpattern at high speed. In adapting this automatic weaving technique tothe production of electrical circuits, wires, indicated by the heavierstrands 21 are interspersed with insulating fibers 22 to form the warp,and another wire 24 is woven back and forth, together with insulatingyarns 26 as the weft, or fill. For purposes to be described hereinafter,it is desired that the fill wires extend outwardly beyond the edges ofthe main part of the fabric and therefore additional warp yarns 27 areprovided at each side of the fabric spaced from the main warp yarns 22to provide supports for the conductive fill wire 24. Nodal points 28 areshown spaced at various places across the surface of the fabric atlocations determined by the pattern automatically woven into the clothin accordance with the circuit with which the cloth is to be used.

A simple form of circuit is shown in FIG. 2 in which a capacitor 29, acoil 31, and a resistor 32 are connected in a closed series loop. Inordinary circuit construction, each of the three electrical componentswould have terminals that would be connected directly to terminals ofthe other two components, or they might be connected by additionallengths of wire if they were too far apart physically to be connecteddirectly together. In the case of printed circuits, the three components29, 31 and 32 would be electrically and mechanically attached by $01-dering to spaced eyelets on the surface of a flat printed circuit boardand would be interconnected by conductive strips running along thesurface of the board.

The components shown in FIG. 2 can be connected by rneans of a matrix ofwires as provided by the fabric of FIG. 1 in a simple manner as shown inFIG. 3. In this case the warp wires are indicated by reference numerals21a-21c, and the fill wires are indicated by reference numerals 24a24f,one for each of the terminals of each of the components. Where theconductive fill wires 2451-241), are to be connected to the conductivewarp wires 21a-21c, the nodal points are indicated by referencecharacters 2811-28), but at other crossings betwen the conductive warpand the conductive fill, no connection is desired. By tracing out thecircuit going from the nodal point 28a through the resistor 32 to thenodal point 28b and thence along the conductive warp 210 to the nodalpoint 28 and so on, it will be seen that matrix circuit in FIG. 3 iselectrically identical with the circuit of FIG. 2.

FIG. 4 shows a more complex circuit, which in this case is aconventional schematic diagram of a monostable multivibrator, theoperation of which will not be analyzed since the circuit is purelyillustrative and does not form a part of this invention. The circuit ofFIG. 4 is transformed into a matrix schematic diagram in FIG. 5 similarto the matrix circuit of FIG. 3 except that it is more complex. Theindividual components are shown connected along both edges of the striprather than along one edge, which permits a significant reduction in thenumber of conductive fill wires required to form the circuit. Forexample if it is desired to connect the components only by means of thematrix circuit and not by direct connection from the terminal of onecomponent to the terminal of an adjacent component, placing thecomponents along only one edge of the woven strip would require oneconductive fill wire for each terminal and a conductive warp wire foreach interconnection between electrically adjacent terminals. Connectingthe components along both edges of the strip can make it possible, intheory, to use as little as half the number of conductive fill wires andone conductive warp wire for each series loop. Of course, in actualpractice, the reduction in the number of conductive warp and conductivefill wires will not normally reach this level but there will still be asignificant saving.

It is not necessary to keep the woven circuit of FIG. 5 arranged in aflat configuration. The woven fabric may be folded or pleated as may berequired to fit the circuit into a limited space and as is shown in FIG.6. While this can be done with the normal point to point connections tosome extent in classical electrical circuits, it is not as simple to doso, and it is impossible to do so in ordinary printed circuits usingrigid boards.

FIG. 7 is a simplified diagram of the conductive fabric of thisinvention. The large circles represent the warp wires 21 in section, andthe small circles represent the warp yarns 22, also in section. Aconductive fill wi"e 24 is shown woven up and over the center warp wireto make a nodal point 28. The insulating fill yarn that is woven withthe warp yarns 22 to make up the insulating portion of the fabric is notshown in this figure, but the location of the warp yarns 22 between thewarp wires 21 and the fill wire 24 does indicate the fact that the warpand fill wires 21 and 24 are basically on opposite surfaces of theinsulating fabric.

FIGS. 8-11 show the cloth from the same point of view as does FIG. 7except that each of the FIGS. 8-11 is spaced one shot, pick, apartmoving successfully down the length of the fabric to illustrate the waythat the warp and fill materials are interwoven. FIG. 8 shows one lengthof insulating fill 26 going across the width of the cloth with alternateones of the insulating warp yarns 22 on opposite sides of the insulatingfill 26, as is common in forming a simple piece of woven cloth. Theconductive warp 21 is shown below the surface of the cloth formed by theinsulating fill and warp, which is basically the preferred location forthe conductive warp so that it will be insulated as well as possiblefrom the conductive fill.

FIG. 9 shows a successive shot in which the shuttle guiding theinsulating fill 26 has moved back from the other side and each of theinsulating warp yarns 22 have been moved to the opposite position thatit occupied in FIG. 8. That is, if a particular warp yarn 22 were abovethe insulating fill 26 in FIG. 8, it is moved down by its headle so thatit is below the insulating fill 26 in FIG. 9. The conductive warp wires21 remain below the level of the insulating warp and fill yarns 22 and26, just as in FIG. 8.

FIG. 10 shows the tie down of the conductive wa p, which must take placeat intervals so that the conductive warp will not become separated fromthe cloth layer. In this figure, the headles controlling the individualconductive warp wires 21 have been moved up so that as the insulatingfill 26 is carried across by the shuttle it will, in effect, follow thepath indicated to bring it below the conductive warp wires and thus tiethem to the fabric. This need not take place at every shot but may takeplace every few shots.

FIG. 11 illustrates a shot in which the conductive fill wire 24 has beenbrought across from one edge of the cloth to the other and in such a wayas to make a nodal point. For this purpose the headle controlling thesecond conductive warp Wire from the left, indicated by referencecharacter 21c, has been moved up out of line with the other conductivewarp wires to permit the conductive fill Wire 24 to pass beneath it.Thereafter on a successive shot, the conductive warp wire 212 will bebrought back into line with its other conductive warp wires and theposition of FIG. 8 will be repeated. It is not necessary that a nodalpoint be made each time the conductive fill 24 is passed across thecloth; there may be occasions, as illustrated in FIG. 1 where aconductive fill will not have any nodal points but will simply connect acomponent on one edge of the cloth with another component on the otheredge.

In order to provide a reliable connection at each of the nodal points 29in FIG. 1, the crossed warp and fill conductors 21 and 24, which havealready been partially crimped in the weaving process just described,are soldered in a continuous batch process. While various forms ofsoldering arrangements may be used, a typical one involves firstcleaning the cloth chemically to remove oil, grease, dirt, and starch.The latter is usually included in yarn manufacturing to serve as abinder for the individual filamerits of the yarn and as a lubricant inthe loom. The fabric i then fluxed, heated, and passed through a solderbath. A thin film of molten solder adheres to the entire length of thewires or, if the wires are stranded, the solder wicks into the Wirewithout clinging anywhere to the insulating yarn or bridging across theyarn from one wire to another. At the nodal points 28, in particular,the solder forms a well filleted joint. After the soldering, the clothis washed to remove the flux and is dried and put back on reels.

In addition to soldering the wires at the nodal points, it is alsopossible to weld the wires since they are directly in contact with eachother.

The next step in the handling of the cloth normally is to apply aplastic material to keep the insulating yarns from spreading apart underflexure and allowing the conductive warp wires 21 and the conductivefill wires 24 to come into contact with each other at points where suchcontact is not desired. Only the yarns and wires in the central portionof the tape as shown in FIG. 1 are normally impregnated. The fill 'wires24 extending beyond the edge of the cloth tape are not coated, and thecoating therefore does not complicate the process of applying terminalsor components to these wires.

The impregnations used vary according to the properties desired. Theelectrical properties, such as insulation resistance and dielectricstrength, and the environmental performance characteristics, such asresistance to moisture and humidity, vibration and temperaturecapabilities, flexural strength, and modulus of elasticity, will dependon this impregnation to a large extent.

Thereafter it is common to sever the conductive fill wires 24 at a pointnear the insulating yarns 27 so that the single conductive fill wire 24shown in FIG. 1 will be divided into a large number of conductive fillwires, each insulated from the others, except where nodal points mayjoin them together through the medium of one or more of the conductivewarp wires 21. In view of the fact that the weaving process is quiteaccurate, the spacing between adjacent conductive fill wires may be veryaccurately determined and, any further accuracy that may be required inpositioning these wires may be obtained by combing them to obtain exactspacings. Certain spacings have been agreed upon as standards in theelectronic industry for producing printed circuits, and these samespacings can be maintained in the woven material of the presentinvention. Moreover the woven material has the advantage that, if thereis a slight digression in the formation of the cloth, such slightdigression may be eliminated by combing whereas in printed wiringboards, nothing can be done to modify the layout, once the boards havebeen printed. A further factor in favor of the woven circuit of thepresent invention is that all that is necessary to change the circuit toinclude or to remove components is to notify the weaver to change theautomatic arrangement of the loom so that nodal points will be made atdifferent locations. In printed circuits, on the other hand, the entireprinted wiring board may have to be completely re-done in order to addan extra component. As a further factor in favor of the woven materialof the present invention, it is possible by means of computer to godirectly from the circuit layout to the loom control to cause nodalpoints to be formed at the desired locations for the bestinter-connection of components. Moreover the basic material used inweaving the fabric of the present invention is quite inexpensive. For

one thing a common form of conductive warp and fill material is copperwire, usually tinned, but not necessarily so, and a usual form ofinsulating yarn is fiber glass. Fiber glass has the ability to stand upunder the heat of the soldering bath better than many other materials,although if lower temperatures are used, other insulating yarns mayprovide other factors that have especially desirable characteristics.And as for the conductive wires, both those for the warp and those forthe fill, they may, as has already been indicated, be either solid orstranded and they may be made of different materials. To take just oneexample, which is not to be considered as limiting, the conductivematerials may be made of nickel iron so as to be able to make connectiondirectly to nickel iron relay terminals without producing a contactvoltage. This can be very important in circuits operating at lowvoltages of the order found in solid state circuits.

FIG. 12 is an illustration of another application of the woven circuitmaterials of the present invention. In this figure two woven circuitpanels have been combined with components in an arrangement which hascome to be called a cordwood type of construction. Electrical componentstoo bulky to be supported easily from the edges of the woven cloth maybe supported from a satisfactory framework, indicated here by referencecharacter 34. If desired the space between the woven circuit panels maybe filled with a foamed-in-place plastic material 36.

While this invention has been described in terms of specific embodimentsit will be recognized by those skilled in the art that the true scope ofthe invention is determined only by the following claims.

What is claimed is:

1. A woven matrix comprising: a plurality of conductive warp members; aplurality of insulating warp members substantially parallel to eachother and forming a first band having a predetermined width and twonarrower bands, one on each side of said first band and spacedtherefrom; a conductive fill member; and a plurality of insulating fillmembers woven with those of said insulating warp members in said firstband to form an insulating fabric and woven with said conductive warpmembers to bind them to said fabric, said conductive fill member beingwoven back and forth across all of said insulating warp members to bebound by those of said insulating :arp members in said first band tosaid fabric, said conductive fill member being spaced from saidconductive warp members by said insulating fabric except at nodalpoints, said conductive fill member being woven into direct contact withsaid conductive warp members at selected intersections to define saidnodal points.

2. A woven matrix comprising: a plurality of conductive warp members; aplurality of insulating Warp members substantially parallel to eachother and forming a first band having a pre-determined width and twonarrower bands, one on each side of said first bands and spacedtherefrom; a conductive fill member; and an insulating fill member wovenback and forth across only those of said insulating warp members in saidfirst band to form an insulating fabric and woven with said conductivewarp members to bind them to said fabrics, said conductive fill memberbeing woven back and forth across all of said insulating warp members tobe bound to said fabric by insulating warp members in said first band,said conductive fill member being spaced from said conductive warpmembers by said insulating fabric except at nodal points, saidconductive fill member being woven into direct contact with saidconductive warp members at selected intersections to define said nodalpoints.

3. The method of forming the woven matrix comprising: placing insulatingand conductive warp members in a loom; moving said conductive warpmembers and selected ones of said insulating warp members in onedirection relative to the remainder of said insulating warp members toseparate said conductive and said selected ones of said insulating warpmembers from said remainder; directing the insulating fill memberbetween the separated warp members; moving said remainder of said warpmembers and said selected ones of said warp members in oppositedirections and directing the insulating fill member therebetween; movingat least one of said conductive warp members relative to the remainderof said conductive warp members; directing the conductive fill memberbetween said one of said. conductive Warp members and the remainder ofsaid conductive warp members to form a nodal point at the intersectionof said conductive fill member and said one of said conductive warpmembers; returning said one of said conductive warp members to alignmentwith the remainder of said warp members; directing an insulating fillmember adjacent to said conductive warp members to anchor the same inplace; repeating the steps of directing said insulating fill member andsaid conductive fill member in a pre-determined pattern to form a wovencloth forming a first band with said conductive fill member woven backand forth and extending outwardly beyond the edges of said first band;providing additional warp yarns supporting said portions of said fillmember extending outwardly beyond the edges of said first band to formtwo narrower bands, one on each side of said first band and spacedtherefrom; removing said cloth from said loom; and anchoring said nodalpoints.

4. The method of claim 3 in which said nodal points are anchored bypassing said cloth into contact with a source of molten solder.

5. The method of claim 3 in which said nodal points are anchored bywelding the respective conductive warp and conductive fill members atsaid nodal points.

References Cited FOREIGN PATENTS 1,346,121 11/1963 France.

DARRELL L. CLAY, Primary Examiner.

L. E. ASKIN, L. H. MYERS, Exam ners.

E. GOLDBERG, Assistant Examiner.

1. A WOVEN MATRIX COMPRISING: A PLURALITY OF CONDUCTIVE WARP MEMBERS; APLURALITY OF INSULATING WARP MEMBERS SUBSTANTIALLY PARALLEL TO EACHOTHER AND FORMING A FIRST BAND HAVING A PRE-DETERMINED WIDTH AND TWONARROWER BANDS, ONE ON EACH SIDE OF SAID FIRST BAND AND SPACEDTHEREFROM; A CONDUCTIVE FILL MEMBER; AND A PLURALITY OF INSULATING FILLMEMBERS WOVEN WITH THOSE OF SAID INSULATING WARP MEMBERS IN SAID FIRSTBAND TO FORM AN INSULATING FABRIC AND WOVEN WITH SAID CONDUCTIVE WARPMEMBERS TO BIND THEM TO SAID FABRIC, SAID CONDUCTIVE FILL MEMBER BEINGWOVEN BACK AND FORTH ACROSS ALL OF SAID INSULATING WARP MEMBERS TO BEBOUND BY THOSE OF SAID INSULATING WARP MEMBERS IN SAID FIRST BAND TOSAID FABRIC, SAID CONDUCTIVE FILL MEMBER BEING SPACED FROM SAIDCONDUCTIVE WARP MEMBERS BY SAID INSULATING FABRIC EXCEPT AT NODALPOINTS, SAID CONDUCTIVE FILL MEMBER BEING WOVEN INTO DIRECT CONTACT WITHSAID CONDUCTIVE WARP MEMBERS AT SELECTED INTERSECTIONS TO DEFINE SAIDNODAL POINTS.